To see this form, click on the Publish... button on the main "Your Puzzles" display. This option is available if you are signed in as a registered player, and the puzzle you have open is one you created.
This is where you can share your puzzle by making it visible to other players when they look at the Puzzle Menus (by clicking the Open... button).
You can make your puzzle visible to all players, or only to registered players.
If you have been playing Chihuahua daily puzzles regularly for some time, you may also see a checkbox labeled "only players with scores similar to yours". This gives you the option of limiting the puzzle visibility to players with a scoring history similar to your own.